The present invention relates to a cutting insert for chip forming machining, the cutting insert including at least one cutting edge created by the transition between an upper face and an edge face of the cutting insert, the upper face being a rake face and the edge face being a clearance face.
In tools for metal cutting having indexable cutting inserts of hard and wear resistant material, the upper cutting edges are subjected to wear and sometimes a portion or all of the cutting edge fractures and collapses. In the case of partial fractures, only the cutting edge collapses without any risk of damage to the tool body on which the insert is mounted. In the case of more extensive insert fractures, the lower portion of the insert may also collapse, whereby the risk of damage to the tool body increases by a considerable degree. That is, if the cutting insert does not rest upon a shim, a major insert fracture often gives rise to damage of the tool body. In order to avoid such damage, it is usual that the cutting insert rests on a shim of cemented carbide. A usual combination is a cutting insert having a thickness of about 5 mm and a shim having a thickness of 3-5 mm. This results in a total thickness of the cutting insert and the shim of 8-10 mm.